Oscillator



April 5, 1938. M, ARTZT 2,113,355

I OSCILLATOR I Filed July 31, 1935 Patented Apr. 5, 1938 PATENT OFFICEOSCILLATOR.

Maurice Artzt, Haddonfield, N. J., assignor to Radio Corporation ofAmerica, a corporation of Delaware Application July 31,

8 Claims.

My invention relates to oscillators. More specifically my invention isan improved form of generator embodying a vibrating member.

One of the objects of my invention lies in the circuits for impressinga. constant driving force on a tuning fork or similar vibrator.

Another object is to drive a tuning fork in such a manner as to hold thefrequency substantially constant.

Another object is to automatically compensate for variations in thepower source.

Further objects will appear in the following specifications and claims.

Figure I is a schematic diagram of one embodiment of my invention, and

Figure II is a schematic representation of a modified vibrating memberwhich may be used in place of the tuning fork of Figure I.

In Figure I a thermally insulated member houses a vibratory member 3.The interior of the housing is kept at uniform temperature by theheating coil 5 which is serially connected through bi-metal thermostat Ito the power source 9. The housing, vibratory member, and heat controlare not, per se, part of my invention. These elements are well known tothose skilled in the art, and, by way of examples, may be of the typedescribed in United States Patent 1,937,583 which issued to Norrman onDecember 5th, 1933, and is entitled Oscillation generator. The Norrmanpatent describes the system as a whole and illustrates compensatingmeans tending to overcome relatively small variations in supplypotential. However, I have found that such compensation means areinsufficient to take care of wide fluctuations in supply and fail toprovide any means for compensating for variations in the cathode heatercurrents. The present invention provides full control over the variablefactors.

In Figure I the power source 9 has its positive terminal connected tothe screen grid ll of thermionic tube l3. The negative terminal of 9connects to the cathode l5 through the self-biasing resistance II, whichmay be by-passed by condenser |9. A suppressor grid 2| is connected tothe cathode I5. The control grid 23 is connected to the primary 21 oftransformer 25 and the remaining terminal of the primary is connected to50 the negative terminal of the source 9. The secondary 29 oftransformer 25 is serially connected to a pair of pick-up coils 3| and33 which are arranged in suitable relation to the vibrating member 3.The anode circuit of tube l3 com- 5 mences with the positive terminal ofsource 9 1935, Serial No. 33,984

which is connected to resistance 35. The resistance in turn joinsinductance 3'! which is connected to anode 39. The anode circuit isconnected through capacity 4| to the primary 43 of transformer 45 whichis connected to cathode l5. The secondary 41 of transformer 45 isserially 5 connected toa pair of driving coils 49 and 5|, and venierresistance 53. The coils 49 and 5| are suitably secured near the ends ofthe tuning fork or vibratory member 3.

The method of operation is as follows: The 10 power is applied at source9. The impulse caused in the anode circuit by the flow of electrons fromthe heated cathode to the anode is transmitted through the capacity 4|and primary 43. The primary in turn induces the impulse in the secondary41 and the serially connected driving coils 49 and 5|. The currentflowing through the driving coils 49 and 5|, which are phased properly,starts vibrations in. the tuning fork. These vibrations induce currentsin the pickup coils 3| and 20 33. The induced currents are properlyphased to set up voltages in the secondary 21 of transformer 25. Thesevoltages are impressed on the control grid electrode, which varies. theanode current. The anode current again induces impulses which drive thefork. The whole process repeats at a frequency determined by theconstants of the vibrating member. The various electrical constants arechosen to aid and reinforce the vibrations. Voltage impulses across 31and 35 may be conveyed to the output terminals 55-5'| by couplingcapacity 59.

The frequency of oscillation of the system as a Whole is not solelydependent upon the natural frequency of the vibrating member. Thefrequency may vary with temperature changes within the housing I. Theuniform temperature control within the housing minimizes this variable.I have also found that if the driving power is not 40 constant butvaries in amplitude, the rate of vibration or frequency of oscillationof the system, will vary.

The applied power impulses may be kept constant in amplitude by choosinga value of resistance 35 in the order of 16,000 ohms and an inductance31 of the order of 30 henries with an RCA Type 89 tube. The magneticcore of inductor 37 is designed to operate at flux values which causechanges in saturation with changing anode current. An increase in anodecurrent slightly lowers the value of the inductance 31 which shifts thephase angle of the current in the inductance with respect to the voltageacross the inductance. The phase angle changes an amount and in suchdirection that increases in voltage of the source 9 which tend toincrease the voltage at the driving coils, are made ineffective, bybeing out of with the currents due to impedance changes in the inductorin the output circuit of the tube. That is, the total efiectiveimpedance of the anode load (inductance Bid-resistance 35) isautomatically varied to compensate for variations in the supply voltagewhich would otherwise impress varying power impulses on the drivingcoils. By properly chosen circuit constants, I have observed linevariations from 95 to 135 volts which caused frequency changes of lessthan one part in a million.

In Figure II I have illustrated a magnetostrictive oscillator. Themagnetic bar 6! extends through the driving coil 63 and the pickup coil55. The terminals of 63 and 65 take the place of the terminals of 38-5!and 3l33, respectively. Oscillators of the magneto-strictive type dependupon the magnetic material expanding and contracting at a frequencyequal to the driving frequency in coil The expansion and contraction ofthe bar Si induces currents of a corre sponding frequency in pick-upcoil 655. In other respects the circuit, and compensating means ofFigure I apply equally to Figure II.

The constant frequency oscillatory currents generated by the circuits ofmy invention may apply to any number of cases when constant frequenciesare required. For example, the oscillations may be used forsynchronizing, television, or timing systems, oscillographs and thelike. The constants and circuits I have set forth are given merely byway of example. I do not intend to thereby limit my invention. Onemodification within the scope of my invention would be to apply thephase change compensating means to the grid circuit of the amplifierinstead of to the anode circuit. Various other modifications will occurto those skilled in the art, without departing from the spirit of myinvention and scope of the claims.

I claim as my invention:

1. In a device of the character described, a source of power subject tovariations, a vibratory member, an amplifier, means for driving saidmember, means including said vibratory member for generating voltages,means for impressing voltages generated by movement of said vibratorymember on the input circuit of said amplifier, and means forautomatically compensating by phase adjustment any variation of power insaid driving means resulting from variations in said source, includinga-magnetic core inductor connected in the plate circuit of saidamplifier, means. for applying a feedback current corresponding to thecurrent derived across said magnetic core inductor to the input of saidamplifi r, and means for adjusting the current flowing through saidinductor to maintain a saturated condition in said magnetic core.

2. In a device of the character described, a vibratory member forgenerating voltages, a source of power subject to variations, anamplifier, means for driving said amplifier, means for impressingvoltages generated by movement of said vibratory member on the inputcircuit of said amplifier, and means for automatically compensating byphase adjustment any variation of power caused by changes in said powersource, including an inductor having a core subject to saturationconnected to the plate circuit of said amplifier, means for applyingfeedback currents corresponding to the currents derived across saidinductor to the input of said amplifier, and means for adjusting thecurrent flowing through said inductor to a range of values insuring asaturated condition in said core.

3. In a device of the character described, a source of power subject tovariations, a vibratory member for generating voltages, an amplifier,means for impressing voltages generated by vibrations of said member onthe input of said amplifier, means in the output of said amplifier fordriving said vibratory member, and means for compensating for variationsin said amplifier output by adjusting the phase relations of voltage andcurrent in said amplifier including a magnetic core inductor. connectedin series in the plate circuit of said amplifier, means for derivingpotentials from said inductor and impressing feedback currentscorresponding to said potentials upon the input of said amplifier, andmeans for establishing the current in said inductor at a value insuringsaturation in said core, whereby the driving power applied to saidvibratory member is maintained substantially constant.

In a device of the character described, a vibratory member includingmeans for generating voltages, an amplifier, means for impressingvoltages generated by movement of said Vibratory member on the inputcircuit of said amplifier, means in the output circuit of said amplifierfor driving said vibratory member, a source of power for said amplifiersubject to variations, and means for compensating for such variationsconsisting of an impedance including a core of saturable material,connected in said amplifier output circuit and to said source wherebythe current in said impedance will have a phase angle which changes withsaid variations to oppose any changes in power in said driving means,and means for adjusting the current flowing through said impedance to arange of values insuring saturation in said core.

5. A device of the character described in claim including an outputcircuit coupled to said impedance.

6. A device of the character described in claim l in which saidamplifier is of the thermionic tube type.

'7. A device of the character described in claim 4 in which saidamplifier is of the thermionic tube type having a cathode energized fromsaid source of power.

8. In a device of the character described, a vibratory member includingvoltage generating means; a thermionic amplifier having cathode, controlgrid, and anode electrodes; means for impressing voltages generated bymovement of said vibratory member on the grid and cathode electrodes;means connected to the anode electrode for driving said vibratorymember; a source of power for said amplifier subject to variations; aninductor connected to said anode, said inductor having a saturable core;a variable resistance connected between said source of power and saidinductor to adjust the currents flowing through said inductor to a valueinsuring saturation in said core, whereby changes in the current throughsaid inductor cause phase angle variations which cause substantialcompensation for variations of power in said source, and means forapplying a feedback cLu'rent corresponding to a current derived fromsaid inductor to the cathode and control grid of said amplifier.

MAURICE ARTZT.

